Klaprothite

Chemical formula: Na<sub>6</sub>(U<sup>6+</sup>O<sub>2</sub>)(S<sup>6+</sup>O<sub>4</sub>)<sub>4</sub>·4H<sub>2</sub>O

Klaprothite is a rare, water-soluble uranyl sulfate, forming tiny, yellow crystals and coatings.

## Characteristics Klaprothite is a secondary mineral from the uranyl sulfate group. It occurs as very small, tabular or bladed crystals, rarely exceeding 0.2 mm in length. It also forms aggregates in the shape of rosettes, acicular aggregates, or thin coatings and efflorescences on host rocks. Due to the small size of the crystals, its features are difficult to observe without magnification. ## Physical Properties Klaprothite crystals are brittle. This mineral is highly radioactive due to the presence of uranium. It is also water-soluble, which is its characteristic and unusual feature. ## Colors and Varieties Klaprothite has an intensely yellow to greenish-yellow color. No varieties are distinguished. ## History and Name The mineral was named in honor of Martin Heinrich Klaproth (1743–1817), a German chemist who discovered the element uranium in 1789. The name was approved by the International Mineralogical Association (IMA) in 2014. It was discovered in the dumps of the Svornost uranium mine in Jáchymov, Czech Republic. ## Uses Klaprothite has no practical or industrial applications. Its significance is purely scientific and collectible, as a rare and well-defined uranium mineral.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
Light yellow
Density
3.29
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification The key diagnostic feature of klaprothite is its water solubility, which is rare for uranium minerals. It is also distinguished by its intensely yellow color, characteristic fluorescence under UV light, and strong radioactivity. It occurs as very small, tabular crystals. ## Distinguishing from Similar Minerals It can be confused with other yellow secondary uranium minerals such as uranophane, autunite, or zippeite. Klaprothite differs from them primarily by its water solubility. Accurate identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms It forms very fine, thin, tabular crystals with a hexagonal or rhombic outline, often elongated and flattened. These crystals group into small rosettes, fan-shaped aggregates, or form thin, dusty coatings.

Geological environment

## Genesis Klaprothite is a secondary mineral, formed as a result of weathering and oxidation processes of uranium minerals (mainly uraninite) in a sulfate-rich environment. It forms on the walls of old mine workings, on dumps, and in the oxidation zones of uranium deposits. ## Mineral Associations It most often co-occurs with gypsum, epsomite, zippeite, uranopilite, johannite, and other secondary uranyl sulfates. The primary mineral from which it forms is usually uraninite. ## Localities The most important and best-documented locality, which is also the type locality, is the Svornost mine in Jáchymov (Krušné Hory, Czech Republic). This mineral has also been identified in the Blue Lizard mine in San Juan County, Utah (USA).

Rarity

Very rare

For collectors

## Quality Criteria Due to its extreme rarity and small crystal size, any well-identified klaprothite specimen is valuable to specialized collectors. Most desirable are specimens with visible, even under a microscope, crystals of good form and intense color, forming rich coatings on a small rock matrix. Contrast with dark host rock enhances visual appeal. ## Popular Localities The only sources of collectible specimens are its two known localities: Jáchymov in the Czech Republic and the Blue Lizard mine in Utah, USA. Specimens from both locations are equally highly prized.

Care and storage

## Cleaning The mineral **must not be wet cleaned** or cleaned with any liquids, as it is water-soluble. To remove dust, compressed air can be used very carefully from a safe distance or a soft brush, keeping in mind the brittleness of the crystals. ## What to Avoid Contact with water, water vapor, and high humidity must be strictly avoided, as these can dissolve and destroy the specimen. Also avoid sudden temperature changes and direct sunlight. Due to radioactivity, direct, prolonged skin contact and inhalation of dust should be avoided. ## Storage Klaprothite specimens must be stored in a dry, airtight container, preferably with a desiccant (e.g., silica gel). It should be kept away from other minerals that may be sensitive to its radioactivity. Always wash hands after handling the mineral.

Sources

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